This invention relates to a primary heat exchanger for use in a multi-poise condensing furnace.
The term multi-poise furnace, as herein used, refers to a furnace that can be orientated so that conditioned return air leaving the furnace may be discharged in either an upward or a downward direction as well as horizontally both to the right and to the left without performing any major modification to the component parts of the unit. Some furnaces are available that allow the unit to be installed in different positions, however, for the most part, these units require extensive modifications to achieve the desired orientation.
Many multi-poise furnaces are equipped with air conditioning units. As a result, condensate can be formed in the primary heat exchanger region due to cool conditioned air being passed over the heat exchanger during the warm months when air conditioning is called for. Similarly, oversizing of the furnace by an installer will result in short on-periods during heating cycles. This does not allow the heat exchanger surface to become sufficiently heated to entirely eliminate condensate that might be present in this area. Underfiring, wherein the gas rate provided to the furnace is lower than the acceptable design rate, can produce the same undesirable result. Slight misalignment of the furnace during installation may also allow condensate to collect in the heat exchanger region. Any condensate collecting in this region can adversely effect the furnace performance and can cause corrosion problems leading to early furnace failure.
It should also be noted that multi-poised furnaces are oftentimes selected for use in applications where available furnace space is limited. The size of a multi-poise unit, to a large extent, is determined by the amount of space required by the primary heat exchanger. Any saving in this regard without sacrificing furnace performance is highly desirous.